APPLICANT'S DESCRIPTION: (provided by Applicant) The overall goals of this core are twofold. The main goal is to provide a mechanism for the larger scale synthesis or resynthesis of intermediates and final products to be used by all of the projects in the grant. An additional goal is to provide a mechanism 1) for the purchase of disposable items for our Analytical Services Group to use for all of the synthetic organic projects; and 2) for defraying the appropriate percentage of maintenance time required for keeping our instruments in top operating condition. As part of this first goal, we will also synthesize needed triphosphates of nucleosides for biological experiments. In the beginning, we need to synthesize the triphosphate of two nucleosides, 4(-thio-ara-C and 2-chloro-2(-deoxy-2(-fluoroadenosine, for mechanism of action studies in Project 16. The triphosphates of other nucleosides will be synthesized as needed.